PITTSBURGH (KDKA) – You may think you’re covered if you have health insurance, but Consumer Reports wants you to think again.

You can easily be socked with huge bills, which is what happened to one woman after her son ended up in the emergency room.

When Christine Knopp’s son, Brendan, got a deep cut on his face, the emergency room doctor offered the option of a plastic surgeon for the stitches.

The surgeon’s bill was $2,900. Christine had assumed her insurance would cover the surgeon, but that was not the case.

“We were pretty shocked. We had no idea that that was going to become our responsibility,” Knopp said.

The problem was that, while the hospital was in the family’s insurance network, the plastic surgeon who stitched up Brendan was not.

Consumer Reports said one of the most common causes of medical sticker shock is going out-of-network.

“A PPO plan might say that it will pay 60 to 80 percent of out-of-network care. That does not mean it will pay 60 to 80 percent of the actual bill, though. It means it will pay 60 to 80 percent of what the insurance company thinks the test or treatment ought to cost,” Nancy Metcalf from Consumer Reports said.

Consumer Reports found lots of examples of patients being hit with astronomical bills, including one woman who was charged $480,000 for back surgery.

“Bottom line, stay in your network. If you must go out of network, research ahead of time what your insurance company will pay,” Metcalf said.